Cardiac patches are engineered materials or tissues designed to repair damage after a heart attack (myocardial infarction). These bio-scaffolds are placed over the injured heart muscle. Their primary purpose is to replace lost tissue and provide structural and functional support to the weakened heart wall. This tissue engineering approach aims to prevent the progressive decline in heart function that often follows a significant cardiac event.
The Biological Need for Repair
A heart attack causes an irreversible loss of cardiac muscle cells (cardiomyocytes) because adult hearts have a limited capacity for regeneration. The body replaces the damaged muscle with non-contractile scar tissue. This collagen-based scar prevents immediate rupture but is electrically inert and mechanically weak. Consequently, the remaining healthy muscle tissue bears an increased workload, leading to ventricular remodeling. The heart muscle stretches, thins, and changes shape, ultimately progressing toward chronic heart failure since the scar tissue cannot contribute to pumping action.
Components and Design
The construction of a cardiac patch involves selecting two main elements: a scaffold and, often, a cellular component. The scaffold acts as the structural framework and must possess specific properties to function effectively on a constantly moving organ. The scaffold must be highly biocompatible and closely mimic the mechanical elasticity of native heart tissue to avoid restricting movement. If the patch is too stiff, it can impair the heart’s ability to expand and contract.
Scaffold materials fall into two categories: natural and synthetic. Natural materials, such as hydrogels composed of collagen, alginate, or decellularized extracellular matrix (ECM), are favored for their biocompatibility and ability to support cell growth. Decellularized ECM is created by removing all native cells from a tissue, leaving behind structural proteins that provide an ideal template for regeneration. Conversely, synthetic polymers like polycaprolactone (PCL) or polyglycolic acid (PGA) are used because their mechanical properties can be precisely engineered for strength and controlled degradation.
Advanced patches often incorporate a cellular component to enhance regeneration. These cells include induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), which are lab-grown heart muscle cells that can contract, or mesenchymal stem cells (MSCs). Some scaffolds are also engineered to be electrically conductive by integrating materials like carbon nanotubes or graphene. Maintaining electrical conductivity is important for integrating the patch with the host heart.
How Cardiac Patches Function
Once implanted over the damaged area, the cardiac patch exerts its therapeutic effects through several mechanisms. The first function is providing mechanical support to the weakened ventricular wall. By acting as a physical splint, the scaffold counteracts pressure that causes scarred tissue to stretch and thin, preventing adverse ventricular remodeling and preserving the heart’s pumping efficiency.
The patch also improves the heart’s electrical function, especially in cell-based or conductive designs. Scar tissue is electrically inert, disrupting the synchronized electrical signaling required for a coordinated heartbeat. Cellularized patches, containing functional cardiomyocytes, aim to establish electrical coupling with the host heart, allowing the patch to contract in sync with the native tissue. Even cell-free patches incorporating conductive polymers can help transmit signals across the damaged zone, reducing the risk of arrhythmias.
A third function is serving as a localized delivery system for therapeutic agents. The scaffold can be loaded with cells, growth factors, or drugs released directly into the injured area. Stem cells housed within the patch release paracrine factors, which are molecular signals that promote the growth of new blood vessels (angiogenesis) and reduce inflammation. This sustained, localized delivery is more effective than simply injecting therapeutic agents, which are quickly washed away by the body’s blood flow.
Current Research and Application
Cardiac patch technology is rapidly moving from preclinical studies toward human application, with many promising candidates in early-stage clinical trials. A significant challenge involves the practical issues of surgical implantation. Because most patches require open-chest surgery, researchers are developing minimally invasive delivery techniques. Examples include injectable hydrogels that solidify in situ or patches delivered via a catheter.
Translational research has demonstrated feasibility in humans, with clinical trials using cell sheets and patches seeded with bone marrow cells. Engineered heart muscle patches derived from donor stem cells have been implanted in patients with advanced heart failure, showing improved function and tissue thickening. These allograft patches offer “off-the-shelf” availability, but they necessitate the use of immune-suppressing drugs to prevent rejection.
Future developments focus on creating personalized patches and ensuring the long-term viability and functional integration of the graft. Researchers are working to overcome the difficulty of achieving full electrical coupling between the patch and the host myocardium, which is necessary for seamless heart function. The goal is to establish a safe, scalable, and effective regenerative treatment that can reverse the progression of heart failure for millions of patients.